Résumé :Caseinomacropeptide (CMP) is a peptide obtained from #-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV)were used...Caseinomacropeptide (CMP) is a peptide obtained from #-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV)were used to digest glycosylated and unglycosylated CMP. Our results demonstrated that whatever was the glycosylated state of CMP, they were digested by BBMV intestinal enzymes, from macropeptides to free amino acids. The digestion of unglycosylated and glycosylated CMP throughout the action of exopeptidases was similar, but the activity of endopeptideases on glycosylated CMPwas limited, certainly due to the attached O-glycosylations. Consequently, much more peptides were identified from the unglycosylated than from the glycosylated CMP. In addition, the glycosylationcore as well as the number of the attached glycosylated chain modified the kinetic of digestion

Résumé :Background: The in vivo quality of milk protein fractions has seldom been studied in humans.Objective: Our objective was to compare the postprandial utilization of dietary nitrogen from 3 [15N]-labeled milk products: micellar caseins (MC), milk soluble protein isolate (MSPI), and total milk...Background: The in vivo quality of milk protein fractions has seldom been studied in humans.Objective: Our objective was to compare the postprandial utilization of dietary nitrogen from 3 [15N]-labeled milk products: micellar caseins (MC), milk soluble protein isolate (MSPI), and total milk protein (TMP).Design: The macronutrient intakes of 23 healthy volunteers were standardized for 1 wk, after which time the subjects ingested a meal containing MC (n = 8), MSPI (n = 7), or TMP (n = 8). [15N] was measured for an 8-h period in plasma amino acids, proteins, and urea and in urinary urea.Results: The transfer of dietary nitrogen to urea occurred earlier after MSPI ingestion than after MC and TMP ingestion, and concentrations remained high for 8 h, concomitantly with higher but transient hyperaminoacidemia and a higher incorporation of dietary nitrogen into plasma amino acids. In contrast, deamination, postprandial hyperaminoacidemia, and the incorporation of dietary nitrogen into plasma amino acids were lower in the MC and TMP groups. Finally, total postprandial deamination values were 18.5 ± 2.9%, 21.1 ± 2.8%, and 28.2 ± 2.9% of ingested nitrogen in the TMP, MC, and MSPI groups, respectively.Conclusions: Our results confirm the major role of kinetics in dietary nitrogen postprandial utilization and highlight the paradox of MSPI, which, despite its high Protein Digestibility Corrected Amino Acid Score, ensures a rate of amino acid delivery that is too rapid to sustain the anabolic requirement during the postprandial period. Milk proteins had the best nutritional quality, which suggested a synergistic effect between soluble proteins and caseins